Conventionally, in the field of metal parts such as steel sheets, bearings, steel balls, and guide rails, a rust-causing factor such as chloride adhere to the parts when they are assembled with bare hands. For this reason, countermeasures such as removal of the rust-causing factors by cleaning and application of a rust preventive oil have been taken. Such rust preventive oils generally contain rust preventive additives (corrosion inhibitors), such as sulfonate metal salts, sulfonate amine salts, carboxylic acids, esters, and amines; however, when workpieces are stored for a long period of time, the addition of the rust preventive additives (corrosion inhibitors) alone may not provide a sufficient rust preventive effect. Therefore, the use of a rust preventive oil that contains heavy components such as wax and petrolatum in addition to the rust preventive additives has been proposed to enhance a rust preventive effect by thickening the coating of the rust preventive oil. (See, for example, Patent Document 1).
Furthermore, since a rust preventive oil containing heavy components such as wax has problems such as increased loss caused by adhesion due to increased viscosity, less degreasing, and deterioration of sprayability in the case of spray coating, a method of maintaining a rust preventive effect of a rust preventive oil by formulating sarcosine-type compounds instead of heavy components such as wax has also been proposed. (See, for example, Patent Document 2).
Also, in a conventional metalworking process, two processes, including a cleaning process and a rust prevention process, were unified, and a cleaning and rust preventive composition that produces both a cleaning effect and a rust preventive effect has been proposed (see Patent Document 3). However, the composition does not exhibit a sufficient rust preventive effect over a long period of time.
As described above, in conventional techniques, a rust preventive oil has not been developed yet that exhibits an excellent rust preventive effect over a long period of time for the parts after various metalworking processes or the metal parts assembled by bare hands when they have a rust-causing factor adhered thereto. Therefore, there is a demand for the development of a rust preventive oil that retains a rust preventive effect over a long period of time.